1. Field of the Invention
The present general inventive concept generally relates to a video signal processing apparatus and method capable of enhancing image sharpness and removing noise. More particularly, the present general inventive concept relates to a video signal processing apparatus and method to remove a noise signal from an incoming video signal and to enhance sharpness of edges of the image signal so as to improve image definition.
2. Description of the Related Art
A cathode ray tube (CRT), which is a prevalent display device, is provided with an electron gun and a phosphorescent surface spaced more than a certain distance from the election gun to deflect an electron beam onto a display area. Accordingly, the CRT has a relatively large volume and a heavy weight in consideration of its screen size. Furthermore, there is a limit in realizing a flat and large-sized screen, and viewers are demanding a high quality and large-scale screen for a display device with the rapid development of technology.
To satisfy the demands of the viewers and overcome the drawbacks of the CRT, a liquid crystal display (LCD), a plasma display panel (PDP), a projection TV, and the like have been introduced. Such display devices can realize a slim, light-weight, and wide screen.
However, the display devices, such as the PDP and the projection TV, having a wide screen, are likely to reproduce an output video signal with a degraded definition due to a noise signal, blurring, and a band-limited signal of an input video signal. In particular, the noise signal in the input video signal causes deterioration of image sharpness and the blurring at edges of the image.
FIG. 1 is a block diagram illustrating a conventional video signal processing apparatus for removing a noise signal.
Referring to FIG. 1, the conventional video signal processing apparatus includes a high pass filter (HPF) 100, a coring part 102, a multiplier 104, a signal delayer 108, and an adder 106. An operation of the conventional video signal processing apparatus of FIG. 1 is described below with reference to FIGS. 2A through 2E.
FIG. 2A depicts a waveform of a signal A input to the HPF 100. As illustrated in FIG. 2A, first and second noise signals n1 and n2 have a smaller amplitude than a normal signal S. The HPF 100 filters the input signal A and outputs a high frequency (HF) signal B illustrated in FIG. 2B.
The coring part 102 prevents a boost-up of the first and second noise signals n1 and n2 in the HF signal B. The coring part 102 outputs a cored HF signal C having components lying outside of a predetermined threshold range −T˜+T with respect to the input signal A, that is, the coring part 102 outputs the cored HF signal C illustrated in FIG. 2C. The HF components of the first and second noise signals n1 and n2, which range within the predetermined threshold −T˜+T, are filtered by the HPF 100 and removed by the coring part 102 as illustrated in FIG. 2C.
The multiplier 104 multiplies the cored HF signal C output from the coring part 102 by a gain having a positive or a negative value. The signal delayer 108 delays the input signal A for a certain time and outputs the delayed input signal A.
The adder 106 adds the signal output from the multiplier 104 with the delayed input signal A output from the signal delayer 108 output signal D. The output signal D output from the adder 105 has a waveform illustrated in FIG. 2D or FIG. 2E. FIG. 2D illustrates the added signal D of the uncored HF signal B and the delayed input signal A, and FIG. 2E illustrates the added signal D′ of the cored HF signal C and the delayed input signal A.
Referring to FIG. 2D, the normal signal S of the input signal A is amplified to the normal signal S′ to thus enhance the image sharpness. However, the first and second noise signals n1 and n2 of the input signal A are amplified to the noise signals n1′ and n2′ as well. Referring to FIG. 2E, the noise signal n1″ and n2″ and the normal signal S″ are not changed substantially from the first and second noise signals n1 and n1 and the normal signal S of the input signal A.
The above conventional video signal processing apparatus enhances a sharpness of a video image by preventing the boost-up of noise signals having a smaller amplitude than a normal signal in the incoming video signal and increasing the amplitude of the normal signal.
However, the conventional video signal processing apparatus is suitable for removing noise from a video signal having a few noise signals, but amplifies noise signals with the edge components accentuated when preventing the boost-up of the noise signals and adding to an original input signal in case of a RF video signal having many noise signals or a HF signal having considerable edge components. Therefore, there is a limit in improving the sharpness and the definition of the displayed image on the screen by preventing the boost-up of the noise signals.